1. Field of the Invention
The present invention relates to a semiconductor device manufacturing line used in a plant for manufacturing semiconductor devices (wafers).
2. Description of the Related Art
Various floor layouts have been proposed for improving the manufacturing efficiency in semiconductor device manufacturing plants. The floor layouts of semiconductor device manufacturing plants are generally classified into two types; centralized type and distributed type.
In an example of a centralized semiconductor device manufacturing line, a rectangular plant floor is partitioned into processing areas, each having a surface area necessary for a specific process. Processing areas typically include a lithography process area, a dry etching process area, a chemical vapor deposition (CVD) process area, a heating process area, an ion implantation process area and a wet process area. Wafers are transferred between any two areas by means of an area transfer mechanism and reciprocating transfer mechanisms within a clean room (see JP-A-4-240714). In another example of a centralized semiconductor device manufacturing line, a plurality of processing areas are surrounded by an extremely clean atmosphere along with an operation area for conducting equipment control and maintenance operations, and a transfer/handling area for transferring and exchanging objects and works to be processed according to processing steps is provided. The operation area and the transfer/handling area are separated from and located close to the process areas (see JP-A-5-90118). An example of the centralized semiconductor device manufacturing lines will be explained later in detail.
In the above-mentioned prior art centralized semiconductor device manufacturing lines, although the number of wet process units is reduced, so that the investment cost can be reduced, when a wet process is carried out immediately before or after other processes, each wafer has to be moved over a long distance between the areas, so that the efficiency is remarkably reduced.
In an example of a distributed semiconductor device manufacturing line, a plurality of equipments for the same step and equipments of different steps are arranged in parallel, so that they may be combined with transfer equipment for continuous processing operations in order to improve the processing efficiency (see JP-A-2-78243). In another example of a distributed semiconductor device manufacturing line, modules of equipments are combined for a series of processing units, wherein the equipments of each module are arranged according to the processing sequence. A plurality of the same modules are provided, and a manufacturing line is established on the basis of modules (see JP-A-6-29368 and JP-A-6-84740). An example of the distributed semiconductor device manufacturing line will be explained later in detail.
In the above-described prior art distributed semiconductor device manufacturing line, although processing operations can be carried out continuously and a wet process can be carried out immediately before and after other processes, it inevitably involves the use of a large number of equipments for a wet process and other processes and hence an excessive cost of equipment investment.
Also, a radially-arranged semiconductor device manufacturing line has been suggested. That is, a control building including a back office is located at the center, and a plurality of independent buildings are arranged radially for respective processing step areas (see JP-A-4-240714). Further, multi-storied semiconductor device manufacturing lines have been suggested. That is, a semiconductor device manufacturing line is realized in the form of a multi-storied building, wherein a vertical transfer system is arranged at the center and processing step areas are arranged radially around the transfer system on each of the stories (Soji Fukuda et al., "Clean Room and Device Manufacturing System of the Future", Ultra Clean Technology, Vol. 4, No. 516, pp. 240-250, 1992, and Kiyoosa Sadohara et al., "Reduction of Cost of Equipments by Local Clean Room", Nikkei Microdevices, pp. 136-141, June, 1995).
In the above-mentioned prior art radially-arranged and multi-storied semiconductor device manufacturing lines, however, wafers have to be moved over a long distance between different process areas as in the case of the prior art centralized type lines so that the operational efficiency is deteriorated when a wet process is conducted immediately before and after other processes. Additionally, since wafers are inevitably crowded in and around the centrally located control building including a back office and the vertical transfer system, the operation of transferring wafers can be time consuming and that of controlling wafers can be complicated.